The heteroaromatic nitriles are valuable intermediates for the preparation of corresponding amides which are used in pharmaceuticals. For example, 3-cyanopyridine is used in the preparation of the niacin or nicotinamide useful for the prevention of pellagra and 4-cyanopyridine is used in the preparation of isoniazid, an anti tuberculosis drug. The heteroaromatic nitrites are hitherto being prepared by a vapour phase reaction of a gas mixture consisting of alkyl substituted heteroaromatic compound, ammonia and oxygen (namely ammoxidation) over a mixed oxide catalyst.